Modifiable Occlusive Skin Dressing

ABSTRACT

Occlusive tissue dressings and methods including an elastomeric drape and a liquid component, at least partially cross-linked at least after one of drying and curing, suitable for application at a dressing-to-skin interface in order to create a substantially air-tight seal. The same or a different liquid component may be applied by a user at a tube-to-dressing interface in order to create a similar air-tight seal around the tube, if not occlusively sealed during its manufacture.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/588,121 filed 18 Jan. 2012.

FIELD OF THE INVENTION

This invention relates to dressings intended to provide afluid-impervious barrier over skin, and more particularly to dressingssuitable for negative pressure wound therapy.

BACKGROUND OF THE INVENTION

Negative pressure wound therapy (“NPWT”) is an effective technology fortreating open wounds. NPWT devices were originally accepted by the USFood and Drug Administration (“FDA”) in 1995, when the FDA approved a510(K) for the Kinetic Concepts Inc. (“KCl”)'s V.A.C.® device. Thedefinition of NPWT devices by the FDA has changed over the years; ingeneral terms, its definition is: a system that is used to applynegative pressure for wound management purposes, including the removalof fluids (i.e., wound exudates, irrigation fluids, and infectiousmaterials). The negative pressure is applied through a porous dressingpositioned into or over the wound cavity, depending on wound type anddepth, or over a flap or graft; the dressing distributes the pressurewhile removing fluids from the wound. NWPT systems typically include:

-   -   Non-adhesive wound dressing used to fill the wound cavity (e.g.,        a sterilized medical sponge or gauze; a.k.a., non-adhesive        packing materials);    -   Drainage tube placed adjacent to or into the dressing;    -   Occlusive transparent film placed over the dressing (and        potentially the drainage tube) and adhered to the skin to        maintain a seal;    -   Collection container for drained fluids from the wound; and    -   Low pressure vacuum source.

NPWT has been approved by the FDA to treat many wound types: chronic,acute, traumatic, sub-acute and dehisced wounds, partial-thicknessburns, ulcers (such as diabetic, venous or pressure), surgically closedincisions (a.k.a., closed surgical incisions), flaps and grafts. Theprescribed therapy time depends on wound type, wound dimensions, andpatient conditions; it typically lasts from four weeks to four months.Disposable dressing components are changed approximately every threedays.

Extensive clinical trials have demonstrated the success of negativepressure in healing the approved wound types by applying a controllednegative pressure typically between 20 mmHg and 200 mmHg. Most studiesapplied a constant vacuum pressure, with 125 mmHg being the most common,although cyclic and intermittent studies are currently underway.Evidence supporting the use of NPWT in the treatment of chronic,non-healing wounds exists primarily in the form of nonrandomized,controlled trials; prospective and retrospective large and small caseseries; single-center studies; and single case studies, with fewrandomized, controlled clinical trials. Studies also exist thatdemonstrate NPWT benefits in healing acute wounds. Additionally, since2006, benefits of managing surgical incisions post-operatively have beenshown with improved clinical outcomes; at least ten studies have beenpublished to date. From these studies, proven medical benefits of NPWTtreatment include:

-   -   Promotes blood flow (perfusion) at the wound;    -   Removes interstitial fluid (a.k.a., wound exudates), reduces        edema;    -   Decreases counts of bacteria and infectious materials;    -   Increases rate of granulation tissue formation, reducing scar        tissue formation, increases growth factors and fibroblasts;    -   Uniformly draws the wound edges together;    -   Provides a protected healing environment; and    -   Provides a moist environment.

Although significant clinical evidence exists to support the benefit ofNPWT as a safe therapy in healing chronic wounds, it is possible duringNPWT to rupture a vein or artery. Usually, a machine safety alarm willsignify a fluid leak rate that exceeds the rate that the machine wasdesigned for. This alarmed leak rate typically includes the combinationof both air and liquid, and typically has an upper safety limit of theminimum blood flow rate possible out of a wound cavity with an activelybleeding vein or artery. If a vein or artery accidently ruptures, thesystem must shut down. Therefore, it is very important to have a safetyfeature that stops blood flow if this occurs, in order not toexsanguinate the patient.

Lina et al. describe in U.S. Pat. No. 7,611,500 and WO1996/005873 aninitial apparatus used for NPWT. In practice, the device proved to beeffective; however, one major limitation was detected: the highelectrical grid power source needed to operate the device limited themobility of a patient. Therefore, future refinements, such as thatdescribed by Hunt et al. in U.S. Pat. No. 6,142,982, incorporatedrechargeable batteries for the power source. Batteries increased patientmobility, but time was limited by the life of the batteries betweencharges. Additionally, battery management became an issue, especiallyfor facilities with a high number of NPWT patients, and electrical gridpower was still needed to recharge the batteries.

Eliminating the need for electrical power, via the grid or batteries,would create a more widely applicable, clinically viable therapy. Thepower requirement variability of a system is dependent on the desiredvacuum pressure, rate of wound exudate removal from the wound cavity,and the leak rate of air into the system. As the air leak rateincreases, more power is needed to supply a continuous negative pressureat a predetermined value or threshold range at the wound bed. Airleakage into the NPWT system requires the most power of any othercomponent. Air leaks are the obstacle to creating a vacuum system thatdoes not require a continuous external power source or frequentrecharging of its internal power storage. Therefore, the feasibility ofa mechanical NPWT system is heavily reliant on the seal quality of everyinterface in the system. The dressing system has been identified as themain source of air leaks in current NPWT systems, particularly at theinterfaces between 1) the dressing and the skin and 2) the tube and thedressing. The amount of air leaks into these interfaces determines thetime frequency that the pump needs to be recharged and the magnitude ofvacuum pressure applied to the wound cavity at a specific time. Thesetwo latter characteristics are dependent system parameters.

Few mechanical NPWT systems are currently available, as described by thepresent inventor in “Development of a simplified Negative Pressure WoundDevice” submitted in 2007 for her Master of Science in MechanicalEngineering at the Massachusetts Institute of Technology. Certainlower-pressure, mechanical devices were disclosed later by Hu et al. inU.S. Patent Application No. 2010/0228205. Current mechanical systemstypically use sophisticated-material, planar dressings, such ashydrocolloid dressings, to try to solve the air leak problem. However,the inherent geometry mismatch of a planar dressing and the contouredskin surface often leads to air leaks. The mechanical devices thereforeare only applicable for select, relatively flat surfaces on the bodyand, even then, it is difficult to eliminate air leaks entirely.

Non-electrical pumps are at the low end of the spectrum of medicalpumps, typically utilizing bladder pumps and capillary action materials.Bladder pumps are used for both extracting and inserting fluids. Bytheir physical characteristics, they are governed by non-linear springlike properties. Currently, bladder pumps are used in wound treatmentsfor drainage purposes, particularly for internal, body cavity drainage.C. R. Bard, Inc. manufacturers many of these non-electrical pumps; onebladder model frequently used to drain internal cavities is commonlyreferred to as a Jackson Pratt Drain.

There are various limitations to applying NPWT with existing mechanical,bladder pumps. There are no pressure gauges on the pumps and, therefore,the user does not know the initial magnitude of the negative pressurepulled, and cannot monitor the pressure during therapy. Additionally,there are no air leak detection systems for the current pumps, except tovisually watch for the expansion of the bladder at a rate higher thanexpected. If the pump is clear, one can also visually monitor if theexpansion rate is due to air leaks or due to drainage fluid.

Capillary action materials are also currently used to treat wounds byproviding very low negative pressure treatment, too low to be consideredNPWT. This form of treatment is usually found in dressings such as smalltopical bandages to provide NPWT-like benefits to very small,self-healing wounds, such as blisters and brush burns. Treating a woundwith this technology enhances the healing environment. Capillary actionmaterials are filled with small capillaries between the wound andoutside environment. A negative pressure is applied by capillary actionof fluid flowing from the wound to the outside environment, thereby,removing interstitial fluid. One example of a capillary action materialis Johnson & Johnson's First Aid Advanced Care Advanced Healing AdhesivePads.

Dressing technologies have tried to address the issue of air leaks intoNPWT systems. This is important to both electrical and mechanicalsystems to reduce their necessary power requirements. In mechanicalsystems, it is necessary for clinically relevant device functionality,such that power input and pump recharge time is reasonable for acaregiver and/or patient to perform. For electrical systems, air leakreduction reduces the number of, if not completely eliminates,false-positive, alarmed emergency system shutdowns. Air leak reductionallows battery designs to last longer on one battery charge and uselower power capacity batteries altogether. Air leak eliminationpotentially eliminates the need for a continuous power supply, as thevacuum pressure can be maintained in the occlusive environment within aspecified threshold, for which the timeframe depends on the pumpparameters and exudate removal rate (typically less than 100 mL/day)from the wound.

Currently, most NPWT dressings (the drape component) are thin, planar,tape-like adhesive dressings that must be applied to a contoured area ofskin. A backing on the dressing must be removed to expose the adhesive,and then the dressing is applied to the skin. The pre-applicationhandling of the dressings alone introduces a probability for air leaks,as the dressing typically folds onto itself or creases very easily dueto its low bending stiffness; many dressings are thinner than a piece ofstandard paper, and the bending stiffness of a material is proportionalto the inverse of its thickness cubed. As a dressing is applied, it mustoften fold onto itself in order to accommodate for a geometricalmismatch between the planar dressing and the contours of the bodysurrounding the wound to be treated. This creates creases, also referredto herein as wrinkles, in the dressing that have a high potential forcausing air leaks into the NPWT system.

Adding to the geometrical mismatch, the dressings often become lessadhesive due to the introduction of foreign materials onto the adhesivebefore dressing application. This is most common and almost unavoidableat the edges of the dressing due to handling by the caregiver. At times,the caregiver's hands introduce enough foreign particles onto theadhesive to forbid further adhesion of that area of the dressing. In theU.S., this often happens when a caregiver uses powdered gloves. This isa critical issue as the edges of the dressing are an area where leakpropagation from the edge of the dressing to the wound cavity ispotentially very high, based on the theory of interface fracturemechanics.

For the electrical NPWT systems, a thin plastic, adhesive backeddressing is typically used. Electrical NPWT dressing systems have notreadily addressed the air leak issues listed above that form at thedressing-to-skin interface. Instead, dressing iterations have focused onair leaks at the tube-to-dressing interface. When NPWT was firstintroduced into the market, the drainage tube was inserted into thewound cavity through the edge of the dressing. This introduced a highpotential for air leaks, which often alarmed the shut-off system.Caregivers began to solve this problem by raising the tube from the skinsurface at the dressing edge, and pinching the dressing under the tubebefore the dressing contacts the skin. This caused the dressing toadhere to itself in an upside-down “T” pattern onto the skin.

Eventually, some of the NPWT dressing, commercial designs incorporatedtheir own solutions to the high air leak rate at the tubing interface.Out of these solutions, the T.R.A.C. Pad by KCI was highly effective,which is driving the current design trends. The T.R.A.C. Padprefabricates the drainage tube to a semi-rigid, tubing connector, whichis then attached to a small, circular, planar adhesive dressing (a.k.a.,drape). All of these connections are made air-tight during itsmanufacture. The tubing does not travel beyond the plane of the adhesivedressing, and therefore its opening remains at the skin surface. Whenthe T.R.A.C. Pad is used, the standard dressing is initially applied tothe wound, without a tubing connection. Then, a small incision is madein the dressing, over the wound cavity; this hole may also beprefabricated into the drape component of the dressing during itsmanufacture. The film backing of the circular adhesive component isremoved from the Pad, and the tube opening is centered over theincision. Since the adhesive surface of the Pad is small, it is easierto handle than the procedure of tunneling the tube into the initialdressing. Although the Pad does not guarantee elimination of air leaksat the tube-to-dressing interface, it highly reduces the probable amountof air leaks into the dressing, based on its ergonomic design and smallprofile. A minimal amount of air leaks is almost unavoidable for allapplications with planar adhesive components, due to the geometricalmismatch and user handling that still remain.

Many efforts have been made in order to overcome the identified barriersof low end, mechanical pumps for application in NPWT. Most of the focushas been on reducing air leaks and creating more predictable vacuumsources. New materials used in NPWT dressings have been the main driverin reducing the air leak rate into the system at the dressing-skininterface. These materials are often not new to wound dressings;however, they are new to NPWT. Pump design has been the focus ofcreating more predictable vacuum sources; mechanical components, such aslinear or constant force springs, are often introduced into the systemand maintain a more predictable behavior throughout therapy.

Only one mechanical NPWT system is on the market today, but is notwidely used: SNaP® Wound Care System by Spiracur (Sunnyvale, Calif.).The SNaP® Wound Care System uses a hydrocolloid dressing with specificmechanical connectors from the tube to the dressing, in order toaccommodate for air leaks; the provided hydrocolloid dressing isrelatively small in size. Hydrocolloids are used in many wound-dressingsystems, and are a common trend in the NPWT market. They are stiffer andthicker than most common, adhesive, planar, NPWT specific dressings.This causes the dressing to fold onto itself less during its handlingand application. However, it cannot accommodate for geometrical mismatchwithout creases, especially as the dressing surface area increases.Since the dressing is stiffer and thicker, these creases are difficultto seal in an air-tight manner, due to its increased bending stiffness.Therefore, hydrocolloids are often only applicable to smaller wounds.Much effort is currently being taken to make them thinner, in order toincrease their applicable surface area and accommodate more forcontours, such as the Replicare Thin Hydrocolloid Dressing by Smith andNephew. Hydrocolloids rely on their extremely sticky adhesive propertiesto account for increased skin adhesion and reduced air leaks. If theycome in contact with wound exudate, the polymers in the hydrocolloidswell with water until saturation, forming a gel, which is held solid inits adhesive matrix structure.

In the SNaP® Wound Care System, the hydrocolloid dressings are connectedto the tubing with a mechanical connector component, similar to theT.R.A.C. Pad, KCI. The SNaP® Wound Care System eliminates any potentialair leaks from this mechanical connector by prefabricating it to thecenter of the entire dressing during manufacture. The prefabricationeliminates any potential air leaks at the tube-to-dressing interface dueto user interface and geometrical mismatch, but it is not capable ofbeing moved on the dressing surface. Therefore, it may need to be placedon an inconvenient area of the wound, such as a location that isuncomfortable for the patient. Additionally, the tube runs parallel tothe plane of the drape; the direction of the tube along the plane of thedrape is fixed. Since the dressings are not typically round, the tubepath may be required to travel in an undesirable path, in order to coverthe wound area with the preset shape of the drape.

For its vacuum source, the SNaP® Wound Care System uses a complexsystem, driven by constant force springs. Therefore, as the pumpexpands, mainly due to air leaks and potentially exudate removal, thepressure remains relatively constant for the length of the pressureapplication. This system is expensive and highly technical when comparedto the non-electrical pumps at the low end of the medical pump spectrum(e.g., bladder pumps); however, it is the first commercial mechanicalNPWT pump, which has been proven to be a potential NPWT pump design.Since air leaks into the dressing system remain highly probable,depending on wound location and caregiver experience, the successfulapplication of the SNaP® Wound Care System is limited in practice.

SUMMARY

Occlusive skin dressings according to the present invention preferablyprovide one or more of the following advantages:

-   -   a conformable dressing system that can be altered if desired and        applied to substantially all areas of the skin surface;    -   a dressing system that is ergonomic;    -   dressings that are easy to obtain and re-obtain by the user,        through conveniences in storage;    -   dressings, pumps, systems, and methods to administer NPWT        without the need for electrical power;    -   minimizing the amount of air leaks into the NPWT system;    -   detecting air leaks into the NPWT system;    -   compatible with light-weight, easily transportable and low cost        pumps; and    -   mechanical methods to minimize the possibility of exsanguinating        the patient.

Occlusive dressings according to the present invention overcome theaforementioned drawbacks by being truly air-tight. One principalapplication of this technology is to facilitate administration ofmechanical NPWT. A liquid component is applied at the dressing-to-skininterface in order to create a substantially air-tight seal preferablyfor at least 48 hours, more preferably for at least 72 hours. Preferablythe same or different liquid component is applied at thetube-to-dressing interface in order to create a similar air-tight seal.In some embodiments, the liquid components may be made of rubberpolymers applied by touch, by squeezing a dispenser, or by spraying thepolymers with an atomization process.

This invention features a kit suitable for occlusively sealing a woundpenetrating the skin of a patient, including a drape formed as a thinsheet of an organic, preferably elastomeric material, substantiallyimpervious to fluid transfer of air and bodily fluids, having first andsecond surfaces. A biocompatible adhesive is at least one of (1)disposed on at least the first surface of the drape and (2) capable ofcontacting at least a portion of at least the first surface of thedrape. When the kit includes the biocompatible adhesive disposed on atleast a portion of the first surface of the drape, the kit furtherincludes at least a first removable liner sheet covering the firstsurface of the drape. In some embodiments, a second removable linersheet covers the second surface of the drape, especially when adhesiveis also disposed on the second surface of the drape. The kit furtherincludes at least one container of at least one sealant component thatis capable of being delivered as a sealant in a liquid state atpre-selected ambient conditions, the sealant as delivered being at leastpartially cross-linked at least after one of drying and curing, andwhich is capable of at least one of drying and curing within thirtyminutes, preferably within twenty minutes and, more preferably, withinten minutes, after application of the sealant as a layer to the edges ofthe drape after the drape is applied to the skin surrounding the wound.

In some embodiments, the drape and the sealant after one of drying andcuring are elastomeric. In a number of embodiments, the drape and thesealant are derived from substantially the same material, such as a typeof a latex compound or a type of silicone compound. In certainembodiments, the adhesive is a silicone-based adhesive and is disposedon at least a majority of each of the first and second surfaces of thedrape as a solid coating or in a pattern such as a grid or concentriccircles. At least one container of a sealant component enables manualapplication of the sealant in some embodiments, such as by squeezing thecontainer and, in other embodiments, at least one container is aremovable vial or cartridge insertable into a dispensing apparatus orother applicator. In a number of embodiments, the kit further includes aflexible tube having a first end and a second end connectable to asource of negative pressure such as a bellows, especially a novelbellows which unrolls, or other mechanical vacuum source. Preferably,the kit further includes a flange having at least one of (1) a centralpassage through which the first end of the tube is insertable and (2) acentral passage communicating with a connector capable of mating withthe first end of the tube. In one embodiment, the first end of the tubeincludes a feature such as a spiral cut to resist blockage of the tube.In some embodiments, the kit includes at least one non-stick handlingcomponent. In a number of embodiments, the kit further includes at leastone wound packing material.

This invention may also be expressed as a method of constructing anocclusive dressing over a wound penetrating the skin of a patient byselecting a drape formed as a thin sheet of an elastomeric material,substantially impervious to fluid transfer, and having first and secondsurfaces. A biocompatible adhesive is selected that is at least one of(1) disposed on at least the first surface of the drape, preferably witha first removable liner sheet covering the first surface of the drapeand (2) applied to at least one of (i) the skin of the patientsurrounding the wound and (ii) at least a portion of at least the firstsurface of the drape. Optionally, a second removable liner sheet coversthe second surface of the drape. The method includes removing the firstremovable liner, if present, and placing the drape onto the skinsurrounding the wound, removing the second removable liner if present,and applying a sealant that is in a liquid state as applied, the sealantbeing at least partially cross-linked at least after one of drying andcuring, on at least the edges of the drape and on the skin adjacent tothe drape in one or more layers. The method further includes at leastone of drying and curing the sealant within thirty minutes, preferablywithin twenty minutes, after application of the sealant to the edges ofthe drape in at least one layer.

In certain embodiments, the adhesive is disposed on at least a majorityof each of the first and second surfaces of the drape, and/or the methodincludes pressing on the second surface of the drape in the vicinity ofany wrinkles in the drape, preferably before sealant is applied in thatvicinity. In some embodiments, a flexible tube is selected having afirst end and a second end connectable to a source of negative pressuresuch as a bellows or other mechanical vacuum source. Preferably, thefirst end of the tube (1) is inserted through a central passage of aflange secured to the drape or (2) is mated with a connector on a flangehaving a central passage communicating with the connector. In oneembodiment, the first end of the tube includes a feature such as aspiral cut to resist blockage of the tube. In some embodiments, thewound is packed with gauze or other fluid-pervious material prior toplacing the drape on the skin.

This invention may be further expressed as a method of constructing anocclusive dressing over a wound, penetrating the skin of a patient, byat least one of (1) packing the wound with a fluid-pervious material and(2) covering at least a portion of the wound with a protective material.The method further includes applying, such as by spraying, anelastomeric material that is in a liquid state, and is at leastpartially cross-linked at least after one of drying and curing, over thepacked material and onto skin surrounding the wound to create anocclusive drape as a thin sheet substantially impervious to fluidtransfer, having a first, inner surface and a second, outer surface. Themethod includes at least one of drying and curing the elastomericmaterial within thirty minutes after application of the elastomericmaterial as a layer.

BRIEF DESCRIPTION OF THE DRAWINGS

In what follows, preferred embodiments of the invention are explained inmore detail with reference to the drawings, in which:

FIG. 1 is a schematic expanded perspective view of a drape, flange andtube with first and second liners prior to application of a liquidsealant according to the present invention;

FIGS. 2 and 3 illustrate a novel first end of the tube of FIG. 1 beinginserted through the novel, preferably symmetrical flange;

FIG. 4 is a schematic perspective view of an alternative novel first endof a tube;

FIGS. 5A and 5B illustrate repositioning of the upright tube into adesired side orientation;

FIGS. 6 and 7 show a drape being covered by an upper liner tomanufacture a dressing according to the present invention;

FIG. 8 shows a hole punched in the dressing of FIG. 7;

FIGS. 9 and 10 shows a tube assembly being inserted onto the dressing ofFIG. 8 with the edge of the flange being sealed to the drape;

FIG. 11 shows a protective liner being added to the dressing of FIG. 10;

FIG. 12 illustrates how a user can cut the dressing of FIG. 11 toconform to a wound;

FIG. 13 shows a handling tab being added to the dressing of FIG. 12;

FIGS. 14 and 15 illustrate debriding and packing an open wound;

FIG. 16 is a perspective view of the underside of the dressing of FIG.11 with the bottom, inner protective layer being removed;

FIG. 17 is a schematic top plan view of a dressing according to thepresent invention attached to skin surrounding the wound;

FIG. 18 is a schematic perspective view of the dressing of FIG. 17 withthe upper protective liner being removed;

FIG. 19 shows liquid sealant being applied to the edges of the drape ofFIG. 18;

FIGS. 19A and 19B illustrate modifying the coverage of a dressingaccording to the present invention;

FIG. 20 is a schematic expanded view of a vial of sealant with anon-stick finger protector optionally positionable within the vial forstorage and transportation;

FIGS. 21A and 21B show a dispensing apparatus with removable cartridgeof liquid sealant;

FIG. 22 is an enlarged perspective view of the cartridge of FIGS. 21Aand 21B;

FIG. 23A is schematic perspective view of a hand-powered squeezeapplicator for liquid sealant;

FIGS. 23B and 23C are enlarged views of the outlet with and without aremovable strip covering the dispensing openings;

FIGS. 24 and 25 are schematic top plan views illustrating non-stickgloves and finger covers, respectively, integrated into a liner;

FIGS. 26-28 are schematic top plan views liners having different shapes;

FIG. 29 is a schematic side view of a dressing according to the presentinvention being applied to the heel of a foot;

FIGS. 30 and 30A are enlarged schematic views of the dressing of FIG. 29with a fold being created and then pressed flat to enhance conformanceto the heel;

FIG. 31 is a cross-sectional view of a known bellows pump;

FIG. 32 is a perspective view of a novel rolling bellows pump;

FIG. 33 is a flow chart of a sample occlusive dressing method;

FIGS. 34A and B are diagrams comparing active versus passive flow NPWTsystems;

FIG. 35 is a diagram of a method to prevent undermining of the dressingdue to exudate build-up in the passive NPWT system;

FIG. 36 is a diagram of some of the specific components of an occlusivewound dressing embodiment;

FIG. 37 is a diagram of a tube connection method with a spiral end tube;

FIG. 38 is a schematic top plan view of the wound shown in FIG. 14 withthe additional step of applying a protective covering over the wound;

FIG. 39 is a view of FIG. 38 with a hole cut in the protective covering;

FIG. 40 is a view of FIG. 39 with a tube assembly placed over the hole;

FIG. 41 is a view of FIG. 40 with liquid drape material applied over theprotective covering and onto surrounding skin to construct a dressingaccording to the present invention;

FIG. 42 is a schematic perspective view of the dressing of FIG. 41; and

FIG. 43 is a schematic perspective view of a novel flange according tothe present invention with integral connector.

DETAILED DESCRIPTION

This invention may be accomplished by a kit, dressing system or methodutilizing a drape formed as a thin sheet of an organic, preferablyelastomeric material, substantially impervious to fluid transfer of airand bodily fluids for preferably at least 48 hours, more preferably atleast 72 hours, having first and second surfaces. Preferably, abiocompatible adhesive is disposed on, applied to or contacted with, atleast the first surface of the drape. In a number of constructions, afirst removable liner sheet covers the first surface of the drape and,optionally, a second removable liner sheet covers the second surface ofthe drape. The invention further utilizes a container of at least onesealant component that is capable of being delivered as a sealant in aliquid state at pre-selected ambient conditions, the sealant asdelivered being at least partially cross-linked at least after one ofdrying and curing, and which is capable of at least one of drying andcuring within thirty minutes, preferably within twenty minutes and, morepreferably, within ten minutes after application of the sealant as alayer to the edges of the drape after the drape is applied to the skinsurrounding the wound.

The occlusive dressings presently disclosed address the power/mobilityand air leak issues by eliminating the need for an electrical powersource and by maintaining reliably air-tight interfaces, particularlyat 1) the dressing and the skin and 2) the tube and the dressing. Thedisclosed dressing systems and their connection methods allow forreliable, mechanical NPWT systems. Not only does this eliminate patientmobility and battery management issues, but it also allows NPWT to beadministered in austere environments, where electricity is often scarceand harsh environments require robust products. Multiple disclosedembodiments support an inexpensive, robust therapy method for globalapplication. Additionally, dressings according to the present inventionare MRI-compatible.

In order to obtain an air-tight skin dressing, the present occlusivedressings use a liquid sealant. This liquid sealant may dry and curefast, even immediately or effectively immediately, upon application tothe skin or other dressing components, into a continuous, occlusive filmor sheet of material. The drying and curing processes may occursimultaneously, may be driven by evaporation, may require a curing agentand/or accelerator, and/or may be enhanced or controlled with a curingagent and/or accelerator. Any extra additives (e.g., curing agents andaccelerators) may be added just before, during, and/or after the sealantapplication process, depending on its chemical reaction with the sealantand its rate.

The liquid sealant bonds to the component(s) that it is meant to seal.The ability of Van der Waals forces to provide the bond strength withoutan added adhesive is based on the material and its thickness.Theoretically, the debond toughness (strength of the bond) must begreater than the debonding energy, and the debonding energy isproportional to: the thickness of the material, the strain in thematerial squared, and the elastic modulus of the material. Specifically(on a first order basis; as its basis is a small strain analysis), thebond strength of a thin film must abide by Equation 1, where Γ is thedebond toughness, ζ is the debonding energy, Ω is a dimensionlessprefactor, h is the thickness of the film, ε_(T) is the strain intension, and E_(f) is the elastic modulus of the film, in order tomaintain adhesion to the skin in tension:

Γ>ζ=Ωhε _(T) ² E _(f)  (1)

Therefore, a highly elastic, thin film presents the ideal materialproperties for reduced, required adhesion strength, increasing thefunctional applicability of the Van der Waals forces.

An additional adhesive, such as a silicone-based, latex-based, oracrylic-based glue, having one or more components, might be employed toproduce the desired bond strength (for example, Liqui-Tape SiliconeAdhesive, Waterproof by Walker Tape Co., West Jordan, Utah). Thisadhesive can be applied under the liquid sealant or chemically mixedwith the liquid sealant prior to its application, depending on itschemical make-up and final mixing properties. When applied under thesealant, the adhesive may need to become tacky (a.k.a., applied settime) prior to sealant overlay. A fast-setting, two-part sealant that ismixed prior to use may be useful in some circumstances, such as SkinTite® silicone available from Smooth On, Easton, Pa., which is ACMICertified Safe and may be used by itself or mixed with a thickener, suchas Thi-vex® thickener, also available from Smooth On. A polymer sealant,or other material with the ability to bond into a continuous occlusivesheet, with adhesive-like properties due to high Van der Waals forcesmay be desirable, where no additional adhesive is needed.

Rubber polymers, such as latex, synthetic rubber, and hypoallergeniclatex, are examples of polymers with desired properties for both thedressing-to-skin and tube-to-dressing interfaces. For example, DeviantLiquid Latex from Deviant, a subsidiary of Envision Design, San Jose,Calif. and Liquid Latex Fashions Body Paint from Liquid Latex Fashions,Warrington, Pa. were both demonstrated to seal the dressing at bothdressing interfaces. The drying and curing time for the latex wassignificantly reduced by applying the liquid to the skin with anatomization process, which is further disclosed in the sections below,by adding alcohol, which helps to absorb the water that evaporates fromthe latex, and/or by flowing a gas across the sealant for convectiondrying. For most applications, the curing/drying time was lowered toimmediately (at most 1 minute) from the 5-10 minutes previously statedby Deviant at http://www.liquidlatex.net/.

Examples of suitable latex materials include Vytex Natural Rubber Latex(NRL), a brand of natural rubber latex produced and marketed by VystarCorporation, Duluth, Ga. Vytex is manufactured by Revertex Malaysia anddistributed by Centrotrade Minerals and Metals, Inc. Protein testresults show that Vytex NRL typically has 90% fewer antigenic proteinsthan Hevea natural rubber latex. Therefore, Vytex causes less exposureand developed latex sensitivities. The Vytex has two products withdifferent levels of ammonia; ammonia is a stabilizer and preservative,and both functionally are feasible for the NPWT liquid sealant and drapecomponents, although alternative stabilizers to ammonia may irritate theskin less. Liquid latex for body painting typically contains ammonia,which is what has been applied to patients during field studies with noirritations. Vytex NRL, low ammonia compound, has provided functional,occlusive drape and sealant components on clean, unwounded skin in a labsetting.

Yulex Corporation, Phoenix, Ariz. creates hypoallergenic latex fromguayule (Parthenium argentatum). Yulex's guayule biorubber emulsions andsolids have none of the sensitizing antigenic proteins found intraditional Hevea latex and is considered a safe alternative for peoplewith Type I allergies. Yulex's biorubber emulsions are registered withthe Personal Care Product Council and its INCI name is Partheniumargentatum Bark Extract. This is a presently preferred material for theNPWT dressing and sealant, in order to provide a non-allergenic materialoption. Yulex presently has ammonia and ammonia-free options.

Synthetic materials such as nitrile rubber and neoprene are alternativesto natural rubber that do not have allergy-provoking proteins, but canalso generally have poor elasticity with higher risk of break rates andviral penetration rates. Therefore, they are less ideal for many of thedressing applications according to the present invention, but may besuitable in some circumstances, particularly for the drape for whichcuring on the skin and drying time are not issues. Other multi-partmaterials, such as Room Temperature Vulcanizing silicones and certainpolyurethanes which are two-part materials with base and curativecomponents, may be acceptable in some applications.

Extremely low stiffness, which is achievable with many rubber-typematerials, increases its bonding ability through Van der Waals forcesalone. The high elasticity capable of being achieved using rubberpolymers accommodates for the high levels of tensional strain reached atthe skin surface during large deformation body movements. Additionally,the material properties of rubber polymers may also accommodate for thetendency to buckle when compressive strains are applied, depending onany initial interface crack sizes and adhesion strength. A desirablesealant accommodates for the large variability over time and surfacearea of the skin surface strains experienced during large deformationhuman motions; in the literature, the maximum large deformation strainis indicated to be approximately 0.45 in tension and 0.3 in compression.As rubber mechanical properties are sufficient to achieve structuralintegrity, the Van der Waals adhesive properties determine theapplicable occlusive sealants, and depending on the polymer, anadditional adhesive may be necessary.

The liquid sealant should have viscosity and curing properties,preferably including minimal shrinkage, that enable it to conform to allcontact surfaces during the application and curing processes, such thatno air leak channels at the interface are present after its application.At the dressing-to-skin interface, the sealant should conform to thefolds and creases in the skin that are often bridged when applying astandard, planar wound dressing. These types of bridged cracks at allcomponent interfaces are often a significant source of air leaks intothe system without a liquid sealant. Once a crack exists, crackpropagation occurs in tension and compression with reduced, appliedstrains, so air leak channels can form overtime with reduced strainmagnitudes. Therefore, eliminating any initial cracks at all of theinterfaces is desirable. At the dressing-to-skin interface, structures,such as hair, often create opportunities for crack propagation and airleaks into a wound dressing, and therefore, hair is often shaved beforedressing applications. The need to shave the hair from an infectiousstandpoint is not desirable, as the shaving process creates trauma atthe hair follicles and increases the risk of infection. With a liquidsealant, these structures can be completely enclosed in the air-tightsealant, and therefore, are not a source of crack propagation under thesealant and do not typically require removal prior to the sealantapplication, as cracks at the dressing edges are most critical to seal,in order to resist crack propagation due to tension. In someconstructions, adhesive on the first surface of the drape issufficiently thick and/or flowable to seal around hairs and skincrevices and to minimize crack propagation.

The sealant thickness, number of components, wound location, and sealantviscosity determines the optimal sealant application method(s). Theliquid sealant may have a very high to low viscosity, as long as it cancompletely wet the contact surfaces. If mechanically applied (e.g.,brush or “painting” application, roller application, sponge/dabbingapplication, squeegee or other squeeze-type application, applicationby-hand (i.e., finger) with or without a non-stick cover, etc.), aviscosity that avoids run-off due to gravity is preferable in order forthe sealant to be ergonomically applicable to any wound location. Thisleads to higher viscosities and is limited at the low viscosity range.Painting is not the preferred application method; when painting thesealant, it is difficult to achieve a constant thickness. If thethickness varies significantly over its surface area, the mechanicalproperties and debonding energy will also vary significantly, which maycause occlusive dressing failure. Painting also has other drawbacks, asit is easy to trap air bubbles in the sealant, which are a source ofcracks for crack propagation. Also, it is difficult to produce andmaintain a very thin coat, which significantly increases the necessaryVan der Waals bonding strength; it increases the stiffness of the finaldressing and decreases its ability to conform to large tissue strains.

Spraying is a preferred method of applying the sealant. Two types ofspraying procedures are possible: 1) an aerosol process which propelsthe liquid sealant with a pressurized liquid or gas propellant thatforces the liquid sealant through an atomizing nozzle, and 2) a shearingprocess which shears the liquid sealant with a pressurized gas or liquidcausing atomization. When atomized, the layer of sealant material can bemade thin enough that run-off is less of an issue, and therefore a rangeof lower viscosities can be used for their desired wettingcharacteristics. Additionally and in combination, the small atomizedparticles fill in the structures on the skin for wetting purposes. Thespraying technique is limited at the high viscosity range, as too highof a viscosity sealant will not be capable of being sprayed withreasonable pressures and velocities for application in the clinicalsetting onto skin. However, this is not seen as a negative aspect sinceliquids with very high viscosities often do not properly wet the complexcontours of the skin surface.

The shearing process may be preferred over the aerosol process. Onereason for this preference is that nozzles clog easily with long polymerchains, unless the liquid can be further thinned. Using the shearingprocess, the shearing fluid and sealant fluid may be kept separate untilthey are both external to the nozzle head. Therefore, internal cloggingof the nozzle does not occur when properly designed, including a fluidfilter (if necessary) and the proper nozzle orifice size. Gas is thepreferred shearing fluid, as it does not add additional liquid to thesystem for drying purposes, it is easy to propel since it can becompressed to high pressure levels, and it helps to dry the sealant whenspraying it onto the skin. Higher viscosities and materials with longpolymer chains are capable of being sprayed by the shearing methodrather than the propellant method, although the viscosities and chemicalchains that can be accommodated with the propellant method can beincreased with complex nozzle design.

Additives such as curing agents, accelerators, convection drying agents,and adhesives may be applied via separate application methods, if theyare not mixed with the sealant prior to application. Their applicationmethod may be via painting or spraying. The application of theseadditive components and the sealant may occur in a multi-step process.They may be stored and applied from separate containers with the same ordifferent application methods in series or in parallel. However, theymay also be applied in parallel or series from the same containing body.One example is a parallel spraying process, for which three ports exist:the sealant port, the shearing fluid port, and an accelerator port;these three components can combine during the atomization process in thespray nozzle where the three ports may interact. Another example is aspray apparatus that allows the amount of sealant (and potentialaccelerator) to be controlled, such that it may be shut-off; theshearing gas then becomes a convective drying gas.

Various polymers with rubber-like properties were determined to have thedesired sealant properties. Additionally, a preferred sealant curesimmediately or within a few seconds after surface contact. With thesecharacteristics, the polymer tends to have long and heavy polymerchains, and therefore, requires the higher atomizing forces capable withthe shearing process. As gas is used to atomize the polymer, there is adesirable range of gas pressure, velocity, and volume flow combinationsthat are required for the desired, continuous-film outcome. Filteredair, pure oxygen, and carbon dioxide are examples of applicable shearinggases that can be readily used, and are often available in the clinicalsetting at the desired pressures and volume flow rates. They are alsoreadily available outside the clinical setting. Using these gases, thenecessary, shearing atomization process is capable of being designedinto a miniaturized handheld device. This process and design is similarto the consumer use of the aerosol embodiment commonly found in consumerproducts and is further disclosed in the Dressing Application Methodssection.

The thickness of a desired seal embodiment can be built-up in asuccessive layered, lamination process. A material that has a strongaffinity for itself with either strong Van der Waals forces or chemicalbonds that form between its layers, such that the final material behavesas a continuous one-layer sealant is desirable. The desired thickness isthe minimal thickness needed for strength and to achieve the desiredocclusive properties, which is material dependent. This thickness isoften thinner than the thickness that can be reliably and uniformlyachieved through a painting process, and therefore a spraying process isoften preferred. The atomization process provides a method to achievethe thinnest functional sealant thickness.

Occlusive dressings are beneficial beyond NPWT and in combination withadvanced NPWT features. Some proven benefits of occlusive properties arehighlighted here. The occlusive characteristic may enhance thepenetration and absorption of topically applied medications, such asointments, powders and creams, which can be beneficial in combinationwith standard wound dressings and with therapies, such as NPWT. TheV.A.C. Instill Therapy Unit (KCI) was meant to combine instillationtherapy with NPWT. Instillation, as defined by the V.A.C. Instilldocumentation, includes both: 1) the introduction and removal of topicalsolutions in liquid form and 2) the ability to flush out and clean awound through a rigorous irrigation technique. The main caregivercomplaint about this and other instillation-purposed dressings is thatthey often leak liquid during the instillation process, especiallyduring a rigorous irrigation procedure, which further induces air leaksduring continued therapy. The occlusive seal and dressings disclosed inthis disclosure would solve any leak issues that arise. Often theirrigation process introduces leaks by propagating cracks in thedressing; by eliminating these cracks, the sealant and dressingtechniques in this disclosure significantly reduce the potential forleaks and leak formation during instillation. The port(s) needed forinstillation fluid insertion and removal can be directly connected tothe disclosed occlusive dressing embodiments with the sametube-to-dressing connection methods that are disclosed in theTube-to-Dressing Interface section in this disclosure.

Although the presently disclosed occlusive dressings were developed withNPWT system in mind, they can be used for any application for which anocclusive (a.k.a., air tight and water tight), air tight, or water tightseal to the skin is desirable. Therefore, they are applicable inmultiple fields beyond NPWT, and more generally in the field of skinsealants and their methods. Truly occlusive dressings create a controlvolume over the area of tissue that they are applied, which is adesirable feature for multiple applications, many which are disclosed inthis application document.

The occlusive dressings discussed in this disclosure are the first skindressings to provide a control volume, as no other dressing to-date isproven to be (reliably) truly occlusive. This would benefit theenhancement of advanced healing therapies that are sensitive to anyvariation in the environment, such as stem cell based therapies, forwhich complete control of the environment is necessary to achievedeterministic results. If a specific air leak is desirable, its rate canbe precisely controlled into the control volume through precisionvalves. Currently, there is no accurate predetermination for the airleak rate into any wound dressing, especially since most dressing airleaks have variability over time and with body movement. Furthermore,truly occlusive dressings may be used in in vivo acute toxicity tests ofdermal irritation and sensitization. The test animal is shaved and thetest material is applied to the skin and wrapped in an occlusivematerial. The skin is then exposed after 23 hours and an assessment forredness and edema is made; this assessment is repeated 48 hours later.

FIG. 1 is a schematic expanded perspective view of a dressing assembly20 including a drape 22, a novel flange 26 and a tube 24 with first andsecond protective liners 28 and 30 prior to application of a liquidsealant according to the present invention. Drape 22 and second liner 30define holes 32 and 34, respectively, through which tube 24 isinsertable.

FIGS. 2 and 3 illustrate a novel first end 40 of the tube 24 of FIG. 1being inserted through the novel symmetrical flange 26 to form a tubeassembly 27, FIG. 3. First end 40, also referred to as distal end 40,includes a spiral extension 42 which, in one construction, is formed bymaking a helical cut into the distal end of tube 24. In otherconstructions, a separate component having a helical shape or othergeometric shape is attached to serve as a deterrent to clogging ofdistal end 40. Spiral extension 42 minimizes possible blockage of lumen46 through tube 24. Another anti-blockage construction is illustrated inFIG. 4 with a tube distal end 60 defining perforations 62 and 64,notches 66 and 68, and a blunt tip 70. Perforations 62 and 64 can beformed as diamond-shaped cut-outs, circular holes, or other geometries.A notch 44, FIG. 2, is also created in this construction to furtherminimize the possibility for lumen 46 through tube 24 to becomeobstructed, as described in more detail below.

Arrow 48, FIG. 2, represents distal end 40 being inserted throughpassage 50 in flange 26 defined by a sleeve region 52, a rotation region54, and an adhesion region 56 having an outer edge 57. Sleeve region 52is adhered to tube 24, as described in more detail below, at a finallocation such as shown in FIG. 3. In another construction, sleeve region52 is attached, via adhesion, welding or other air-tight connectionprocess, to a short piece of tube with a connector that connects to alonger piece of tubing. In yet another construction, the flange includesan integral connector capable of mating with flexible tubing such asshown in FIG. 43. Rotation region 54 serves as a flexible ball joint inthis construction. As depicted in FIGS. 5A and 5B, tube 24 can bemanipulated in the direction of arrow 72, FIG. 5A, to a desired sideorientation as shown in FIG. 5B. Lumen 46 through tube 24 remains openin some constructions because distal end 40 extends beyond adhesionregion 56, with notch 44 preferably below sleeve region 52 but aboveadhesion region 56, so that rotation region 54 does not collapse ontoitself. In other constructions, the flange is sufficiently short andwide to minimize the possibility of pinching closed. Sleeve region 52 issealed in an air-tight, fluid-impervious manner in some constructions byfirst applying a silicone adhesive, such as Liqui-Tape adhesive fromWalker Tape Company as mentioned above, to the portion of the outersurface of tube 24 which will be brought in contact with sleeve region52 during assembly. A liquid sealant can be applied to the junction oftube 24 and flange sleeve region 52 to further occlude possible fluidescape at that junction.

In some constructions, flange 26 is manufactured directly onto tube 24,via a dipping, molding or spraying process. In constructions whereflange 26 is constructed entirely from, or coated with, a material thathas an affinity for itself, sleeve region 52 may self-adhere to rotationregion 54 and adhesion region 56, to the extent that region 56 isexposed, when folded against itself as shown in FIG. 5B. Where thematerial forming the exterior of flange 26 has an affinity for thematerial of drape 22, especially for materials containing latexcompounds, the exterior of sleeve region 52 will also adhere to drape 22at least to some extent; latex-type material applied to the surface oftube 24 will further enhance this adhesion. Fixing the tube 24 into afixed orientation such as shown in FIG. 5B may be especially beneficialfor bed-ridden or less mobile patients so that the tube can bepositioned to avoid the patient lying on the tubing for long periods oftime or to avoid compromised areas around the wound. In othercircumstances where the tube remains movable, it can be easilyrepositioned because rotation region 54 remains flexible and the tubecan be monitored and moved frequently to assure that tissue is notdegraded from lying on the tube in one position for an extended period.Especially for active patients, the tube 24 can be periodicallyre-positioned by the patient or by a healthcare professional.

FIGS. 6 and 7 show a drape 22 being covered by an upper liner 30 tomanufacture a dressing according to the present invention. Preferably,drape 22 has a thickness ranging from 2 microns to 0.4 mm, especially inportions which will be applied to skin; a greater thickness in thecenter portion to be located over a wound is less critical forocclusivity. In some constructions, adhesive is pre-applied on theupward-facing surface shown in FIGS. 6 and 7, which will be placed incontact with skin during use; in other constructions, adhesive is alsoplaced on the opposite side of drape 22, to be covered by liner 30, asindicated by arrow 81 in FIG. 6, for storage and handling. The adhesiveis applied as a uniform coating in some constructions and, in otherconstructions, as concentric circles or other non-uniform pattern.Preferably, liner 30 has extensions 82 and 84 which extend beyond thedrape 22 to facilitate handling of the dressing without touching anyadhesive, and to enable easy removal of the liner 30 from the drape 22after placement on a patient.

FIG. 8 shows a hole 32 punched in both layers of the dressing of FIG. 7.Hole 34, FIG. 1, is not visible in FIG. 8.

FIGS. 9 and 10 shows a tube assembly 27 being inserted, arrow 90, ontothe dressing of FIG. 8 with the adhesive region 56 to edge 57 of theflange 26 being sealed to the drape 22 utilizing the pre-appliedadhesive. Additional adhesive or sealant can be added around edge 57 orpre-applied to region 56 as desired.

FIG. 11 shows a protective liner 28 being added to the dressing 20 ofFIG. 10. Protective liner 28 protects the skin-side adhesive, whenpre-applied, until liner 28 is removed as illustrated in FIG. 16 below.Distal end 40 with anti-clogging feature 42 is sufficiently relaxed andshort in length to be contained under liner 28. Liner 28 preferablyextends beyond drape 22 over regions 82 and 84 of liner 30.

FIG. 12 illustrates how a user can cut the dressing 20 of FIG. 11, alongdashed line 92 using scissors 93 for example, to conform to a wound.

FIG. 13 shows a handling tab 94 being added, arrow 96, to the dressing20 of FIG. 12, which is especially useful if liner extensions 82 and 84are cut away. In this construction, tab 94 is attached by adhesive 95 toone of liners 28 and 30 to assist removal of the selected liner.Additionally or as an alternative, perforations 97, 98 create locationsfor easy removal of the liners. If perforations are utilized, it ispreferred that the top and bottom liners have perforations that arealigned along different angles. The preferred angle difference issubstantially perpendicular, that is, at about ninety degrees offset.Perforations are preferred when extensions 82, 84 are not provided. Thedressings are very difficult to handle with medical gloves on, which arerequired for sterility. Therefore, handling tabs eliminate the need forthe clinician to touch the adhesive. This is also desirable sincepowdered gloves tend to cause the adhesive to adhere to the powder andloose its adhesion properties. Another solution would be to providenon-stick finger or hand covers, such as shown in FIGS. 24 and 25,similar to the finger sealant applicator shown in FIG. 20. This isespecially important when dressings are re-shaped, potentially cuttingoff handling features, and when the user is removing the top protectiveliner and folding down the top folds. Ideally, additional handlingcomponents are built into the packaging components or protective liners.Such as, the package that the drape comes in, turns inside out to form asterile, handling glove, or the bottom liner is used to maneuver thehigher-level of adhesive interactions when dealing with the top liner.The bottom liner may have a cut-out (pre-perforated) glove, FIG. 24,with the non-stick side, e.g. silicone-coated, initially facing theadhesive; preferably, a non-stick coating is provided on both sides forboth right- or left-handed application.

FIGS. 14 and 15 illustrate debriding an open wound W and cleaning thewound cavity and surrounding skin SK, preferably at least 3 cm in widthas indicated by dashed line 102, with standard cleaning methods such aswith alcohol and gauze wipes. Typically, the next step is to pack theopen wound W with fluid pervious material 104 such as gauze, open-cellfoam or a sponge.

FIG. 16 is a perspective view of the underside of the dressing 20 ofFIG. 11 with the liner 28 being removed as indicated by arrow 106, suchas by pulling on corner 108, to expose drape 22 with pre-appliedadhesive.

FIG. 17 is a schematic top plan view of a dressing 20 according to thepresent invention attached via adhesive drape 22 to skin SK surroundingthe wound. When negative pressure therapy is desired, a source ofnegative pressure is connected to tube 24 such that its lumen is incommunication with the wound cavity.

FIG. 18 is a schematic perspective view of the dressing 20 of FIG. 17with the upper protective liner 30 being removed, as indicated by arrow110. Dashed line 112 represents a perforation or pre-cut line to assistremoval of liner 30 without sliding it over tube 24.

FIG. 19 shows liquid sealant 114 being applied to the edges of the drape22 of FIG. 18. The preferred sealant embodiment has as width of 2-3 cmand is centered over the edge of the drape 22.

If the dressing is applied to contoured surfaces on the body, such asdescribed below in relation to FIGS. 29-30A, folds in the planardressing may be necessary for adhering to the surface of the skin, inorder to match the surface contour. These folds typically travel fromthe outer edge towards the tube 24. In this situation, the preferredapplication method is to minimize the number of folds by creating a fewlarge folds. Preferably, there are no more than four folds, dividedsubstantially equally around the periphery of tube 24. These folds arecreated when adhering the drape to the surface of the skin, forming a“T”. Then, when the top protective liner is removed, the folds areadhered to the surface of the drape with the adhesive on the top of thedrape. Preferably, the folds form individual triangles on the topsurface of the drape. The folds are then pressed to lie flat and becompletely adhered to the surface of the drape. Sealant is then appliedto the edge of each fold to seal off the area between the fold and thetop of the drape from the surrounding environment. This additionalsealant preferably connects with the sealant placed around the outeredge 114, FIG. 19, for example. Preferably, the additional sealant isapplied at substantially the same time as the original sealant with thesame sealant material. Any drape material that would extend onto theskin, beyond the original edge of the drape, when folded preferably iscut off before pressing the folded drape material against the skin tolie within the original edge of the drape. Patterns may be provided onthe upper protective liner to direct the user where to put the folds,when needed.

FIGS. 19A and 19B illustrate modifying the coverage of a dressing 20 aaccording to the present invention, with drape 22 a, tube 24 a andflange 26 a. If the dressing 20 a is too small to cover the desired skinarea around the wound, preferably by 3-5 cm, for instance if the usercut away too much of the dressing, as shown by cut-out 120, whilereshaping the drape for easier application or in order to avoid acomplex contour near the wound cavity, the user can use sealant toreconstruct the dressing as shown by additional sealant 122, FIG. 19B. Amodified occlusive dressing 20 a is thereby achieved. However, it ispreferable for the drape 22 a itself to cover the entire wound edge, inorder to protect the wound cavity from the sealant material.

FIG. 20 is a schematic expanded view of a vial 130 of sealant, withclosure threads 131 to receive a cap 134, with a non-stick fingerprotector 132, shown in cross-sectional view, preferably with a rim 133,optionally positionable within the vial 130 for storage andtransportation.

FIGS. 21A and 21B show a dispensing apparatus 140 with removablecartridge 150 of liquid sealant. Dispensing apparatus 140 has a fingertrigger 142 and a nozzle 144 in this construction and can be powered bya cylinder of compressed gas, such as a CO2 cartridge, contained withinthe housing 146. Preferably, the apparatus is gravity fed. Because thereneed not be a needle valve, such as found in typical air guns to stopthe flow of fluid, an adhesive tab 152, FIG. 22, is initially removedfrom tip 154, and the cartridge 150 is inserted into the apparatus 140as represented by arrow 149, FIG. 21B. A plug 156, FIG. 22, is thenremoved, such as by twisting, to expose an air hole at the top ofcartridge 150 and activate apparatus 140 and allow sealant to flow or besprayed out of nozzle 144. The apparatus 140 can be set asidetemporarily, with nozzle 144 directed upwards, between sealant layerapplications.

FIG. 22 is an enlarged perspective view of the cartridge of FIGS. 21Aand 21B with internal chamber 160, raised floor 162, and slope 164 inthis construction to assist gravity feed of sealant liquid to tip 154,as indicated by arrow 166. In other constructions, a multi-componentsealant is delivered utilizing a separate chamber for each component.The components are mixed during delivery in a down-stream mixing chamberor in a mixing nozzle such as the 3M™ Scotch-Weld™ EPX™ Mixing Nozzlecurrently available from 3M Company, St. Paul, Minn. Othermulti-component delivery systems can be utilized such as thosecommercialized by Henkel Loctite Corporation, Rocky Hill, Conn. One ormore of the sealant components can be a powder or other state as long asthe final sealant is delivered in a liquid state, including as liquiddroplets via shearing or a propellant.

FIG. 23A is schematic perspective view of a hand-powered squeezeapplicator 170 for liquid sealant.

FIGS. 23B and 23C are enlarged views of the squeegee-type outlet 172with and without a removable strip 174 covering the dispensing openings176 of passages 178 communicating with inner chamber 180. In thisconstruction, a removable tab 182, FIG. 23A, allows air to enter chamber180 during delivery of the sealant.

FIGS. 24 and 25 are schematic top plan views illustrating non-stickgloves 191 and finger covers 201 formed in liners 190 and 200,respectively. These applicators are non-stick, such as by a non-sticksilicone coating, on only one side in some constructions and, in otherconstructions, are non-stick on two sides.

FIGS. 26-28 are schematic top plan views liners 210, 220 and 230 withindicator lines 212 and 214, 222 and 224, and 232 and 234, respectively,having different shapes for selected locations and contours of apatient. Shorter lines 222 and 234 have priority if folds are needed; asymmetrical shape such as a square or the circular shape of liner 210,FIG. 26, has fold lines of equal priority.

FIG. 29 is a schematic side view of a dressing 20 b according to thepresent invention being applied to the heel H of a foot F. Flange 26 bis positioned with tube 24 b communicating with a wound in heel H. Onelarge fold 240 is shown, with edges 244 and 246.

FIGS. 30 and 30A are enlarged schematic views of the dressing of FIG. 29with a fold 240 being created and then pressed flat to enhanceconformance to the heel. All edges 242, 244 and 246 should be sealedwith sealant 248 according to the present invention.

There are multiple different methods of using the sealant described inthis disclosure at the dressing-to-skin interface. The first method isto use the sealant in conjunction with current, commercial skindressings (or dressings with similar embodiments), in order to achieveocclusive properties. In order to do this, the dressing is first appliedto the skin, step 1502, FIG. 33, after the wound is packed, step 1501;typically, the dressing (a.k.a., drape component) is a planar adhesivetape form. The drainage tube may enter into the dressing at thedressing-to-skin interface, or it may have its own connector thatrequires an incision into the dressing above the wound cavity, step1503. The dressing system is applied with its recommended procedure.Then, all dressing-to-skin interfaces are sealed with the sealant andpotentially additional adhesive, step 1504.

At the dressing-to-skin interface, the sealant contact with the skinshould be biocompatible. The sealant should conform to and seal off thefolds and creases in the skin, which are often bridged when applying astandard, planar wound dressing. These cracks are a significant sourceof air leaks into the system without a liquid sealant with the properwetting properties. The proper wetting properties are achieved byapplying the liquid sealant directly to the skin and dressing in itsliquid form through a painting process or through spraying the liquidwith an atomization process that eliminates liquid run-off and that mayachieve a more uniform, thin film.

Once a crack in the planar dressing exists, crack propagation may occurin tension and compression with reduced, applied strains. Therefore,sealing any initial cracks in the dressing-to-skin interface isdesirable. Also, properly sealing the dressing-to-skin interface at theedge of the dressing deters any air leaks from future crackpropagations, as the sealant hinders the propagation from reaching theoutside environment. If an additional adhesive is used between thesealant and dressing-to-skin interface, then the adhesive should adhereto the skin, dressing, and sealant to form the necessary bond strength.The adhesive or its applied components should also conform to the foldsand creases in the skin and/or dressing. The adhesive should becompatible with the skin, dressing, and sealant when applying theadhesive under the sealant, or when mixing the sealant with an adhesivecomponent prior to application.

Use of the liquid sealant can permit elimination of the currentcommercial dressings (or similar dressing embodiments; a.k.a., the drapecomponent). The liquid sealant can be applied directly over the woundcavity and wound packing material. In some embodiments, the packingmaterial may require an additional liquid tight barrier if the liquidsealant can be absorbed into the packing material. Additionally, aliquid tight barrier may need to exist at the interface between thepacking material and the wound edge, as the sealant could potentiallyleak into this barrier, depending on the application technique of thepacking material, which may not be desirable. A gap at the interfacebetween the packing material and the wound edge may be disruptive to thesealant in creating a continuously occlusive film, or the potential ofthe sealant contacting the inside tissue of the wound cavity may need tobe eliminated. These barriers may be of an occlusive nature; in thiscase, the sealant should be applied at any of their non-occlusive edges;however, the sealant may also cover the entire surface area, which mayhelp to maintain the adhesion of the barriers. The barriers can be madeof multiple materials from adhesive and non-adhesive polymer films toclays and pastes, for example. Barriers mentioned in this descriptionare different from the standard wound dressings, as the standard wounddressings' adhesion to the skin forms structural and adhesionintegrities of the dressing-to-skin interface, and the barrierscurrently discussed are used to protect the wound from the sealantcomponent and are not necessarily intended to provide any structuralsupport beyond that purpose.

Maceration of the skin under a truly occlusive dressing may be ofconcern to the caregiver. This can be solved with a material selectionsolution, as a one-way, directional occlusive sealant material can beused that allows the skin to breathe and its moisture to evaporatewithout letting air into the system. Similar material properties arecommonly found today in materials used for sports apparel. Additionally,this can be solved from a design perspective. The sealant applicationarea can be made narrow enough that the moisture of the tissue under thedressing can diffuse around the seal. If a larger surface area of sealadhesion is necessary, a web of sealant can be applied to allowdiffusion around the webbing. Additionally, the sealant can vary inthickness via the atomization process, where a thick enough dressing forocclusive properties is sprayed around the wound edge ordressing-to-skin interface. This application can maintain a narrowwidth, and then the rest of the dressing can be made into a thinnerlayer that is breathable based on a different number of laminationlayers or by using different spraying variables and techniques. Thisthinner part of the dressing can maintain a continuous film embodimentwith the occlusive barrier, as the debonding energy of the thinner partis significantly decreased due to the reduction in thickness, increasingthe effective bond strength. Additionally, this breathable component canbe webbed over the surface, instead of encompassing a continuous filmembodiment.

The tube-to-dressing interface should be sealed if the connection is notprefabricated to be occlusive during its manufacturing process, as it isin the Spiracur dressing. The sealant should bond to both materialsfound at the tube-to-dressing interface and form an occlusive sealspanning the interface, step 1504, FIG. 33. Three methods can be usedfor this sealant interface and its components: 1) dressing componentsthat were not originally prefabricated to be occlusive can bepre-assembled and sealed prior to dressing application (most desirablefrom an occlusive results reliability perspective); 2) dressingcomponents can be preassembled prior to dressing application, but theseal is applied after dressing application; or 3) the tube connectionmethod is fabricated and sealed to the dressing during or post dressingapplication.

The first method provides the user with a method to prefabricate acustom dressing that has an occlusive tube-to-dressing interface. Thiseliminates many potential air leaks, and for the first time, allowscustom, prefabricated, occlusive dressings to be made in the clinicalsetting. Method two is convenient if the liquid sealant is the same forall dressing interfaces; therefore, all the interfaces (tube-to-dressingand dressing-to-skin) can be sealed in one step after the dressingapplication. However, this method requires that the pre-assemblyconfiguration is stable during its application, before any sealant isapplied. For method three, less prep-work needs to be performed by thecaregiver. If this sealant method is ergonomic and repeatable withoutany prefabrication, then this method can significantly cut-down ondressing time, which is a significant personnel and cost savings for thecare center. The ergonomic and repeatable characteristics depend on thetubing connector designs.

Multiple tubing connector designs can be manufactured for sealingpurposes to be used for all three methods. Three basic design conceptscan span many embodiments. These three design concepts are:

1) Puncture the dressing with the drainage tube, such that the drapefits snuggly against the tube. Then, apply the sealant at thetube-to-dressing interface. With this method, the tube can recess intothe wound cavity at a custom length as indicated by extended distal end1801, FIG. 36. If the adhesion force of the sealant needs to beincreased, an additional adhesive can be added under the sealant ormixed with the sealant, or the tubing and/or dressing can be pre-coatedwith a material that the sealant has an affinity for. In practice,rubberized polymers typically have a strong affinity towards themselves,even if the under layer is previously cured. Multiple drainage holes, asillustrated in FIG. 4, or a spiraled cut pattern, FIGS. 2 and 3, in theportion of the tube extending into the dressing is preferred, in orderto prevent the tube from occluding against saturated packing material orwith particles in the wound exudate.

2) The same concept as in concept 1, except with a different tube entryinto the dressing. This concept is for the case where an initial planardressing is used. Two pieces of the planar dressing cover the wound fromtwo different sides, and they meet above the wound cavity in a “T”joint. The tube is placed through this “T” joint into the wound cavitybefore the “T” joint is sealed. Then, all of the interfaces are sealedwith the liquid sealant.

3) The same concept as in concept 1, except at the tube-to-dressinginterface, a prefabricated foot 1802, FIG. 36, also referred to hereinas a flange, is attached (preferably air-tight) to the tube in order toprovide a planar surface to seal to the dressing. In one functionalembodiment, the foot 1802 is made of a flexible material that thesealant has a strong affinity for and no additional adhesive isnecessary. The material of the foot may be tapered in thickness, suchthat it thins to meet at its edge(s) with the dressing, which may bemore desirable for reliable, occlusive sealant application. The tube canconnect to this foot 1802 in many orientations; however, it is oftenpreferable to minimize the dressing profile. However, often whenminimizing the dressing profile, the tube is in an orientation thatcannot be readjusted after dressing application. Therefore, the tube mayconnect perpendicular to the skin surface, and by using non-kink tubingand/or the flexibility of the foot 1802 material allows the tube to beoriented in any orientation post dressing application, such that thetube will not kink and occlude itself. For this concept, the tube maynot puncture the drape, but instead, the hole (a.k.a., incision) may bepre-cut; the foot should extend beyond the hole (a.k.a., incision).

4) The fourth concept is the similar to concept 3, except the tubingdoes not extend into the wound cavity, FIG. 37. Therefore, an incisionis made into the dressing, and the tube opening is positioned over thecenter of the incision, as in the T.R.A.C. Pad. The foot should extendbeyond the incision and is sealed to the dressing with the liquidsealant or occlusively pre-sealed during its manufacture. In thisembodiment, the end of the tube should be designed to stop potentialocclusion onto the foot, onto packing materials, or with wound exudatesubstances. Therefore, if the foot is connected to the tube above theskin surface, the end of the tube may have a spiral cut along itslength, up to its interface (intersection of the upper portion of foot1802 and tube distal end 1901 in FIG. 37) with the foot. Additionally,an anti-occluding material may be placed at the end of the tube betweenthe foot and the dressing. This anti-occlusive material may be a largepore, open cell sponge.

In the tube-to-dressing connection, as with all sealed interfaces, anadditional adhesive may be added if the bonding strength needs to beincreased. The foot may also be initially adhered with a tape oradhesive to the dressing prior to sealant application. The tubeconnectors can exist in many similar embodiments to those listed above;however, a limited number of examples are given here in order toillustrate the basic connections and the occlusive dressings. Thetube-to-dressing interface may be occlusively pre-sealed during itsmanufacture. Additionally, the component attached at the interface mayonly consist of a tube connector (which may or may not contain a segmentof tubing) that is additionally connected to a longer piece of tubingthat then attaches to the pump. Examples of occlusive tube connectorsare barbed connectors that connect directly with a tube, specificconnectors that interlock with each other and are required on each endof the connected components, and a compression fit seal such as acylindrical hole in rubber that the tube can be occlusively pressedinto.

As previously stated, handling a dressing with a planar tape embodimentmay cause the adhesive to weaken prior to dressing application.Therefore, specific handling devices for the caregiver can be includedwith this dressing component. These devices may include non-stickgloves, such as PTFE gloves, FIG. 24, or non-stick fingertips, FIGS. 20and 25. Handing tabs that extend from the dressing may also beincorporated into the dressing design. These tabs may be a part of thedressing (a.k.a., drape) that are torn-off after applying the dressing,or they may be extensions of a removable backing material that isattached to the dressing as shown in FIG. 13.

For application of the sealant, many application embodiments and methodsare possible. For mechanical applications, including paintedapplications, the applicator embodiment can be a brush, roller, sponge,spatula, or other similar embodiment to apply paint in a “spreading”fashion. These spreading devices can be attached to a container(preferably refillable) of liquid sealant for a continuous feed ofsealant to the applicator; this may be gravity fed (passive or usercontrolled), or the applicator may be prepped with sealant by dippingthe applicator into a container of sealant. Although painting is not thepreferred application method for the liquid dressing, it may bepreferred if a high viscous sealant material is used to span large gaps,such as that between the packing material and the wound edge, thepotentially high ridges of a hydrocolloid at its skin interface, or thelarge creases, gaps, and folds in a hydrocolloid dressing, due to itshigh stiffness and thickness and geometrical mismatch.

For sprayed applications, the device to atomize the sealant with ashearing process can be a refillable spray gun or airbrush, with anexternal pressurized gas supply, or this functionality can beincorporated into a miniature, handheld spray can, which can berechargeable and refillable. Each embodiment has a design specificenvelope of pressure, velocity and volume flow of gas that is requiredto shear the sealant, such that it forms a thin film, continuous layeron the skin. If the operation is outside the envelope, the droplets ofthe spray may be too large and will not spray as a continuous layer, butwill sputter onto the skin, or the gas may not shear the fluid out ofthe fluid opening. In a functional embodiment, the liquid sealant isgravity fed into a center opening in a nozzle, and pressurized gasshears the sealant through a circumferential ring around the sealantnozzle opening. Multiple nozzles may exist for one or both fluids.Particularly, the spray pattern may be controlled through the shearingof the sealant from multiple gas ports, aimed in different shearingdirections across the liquid sealant nozzle. In a handheld device, thepressurized gas may be generated from a miniature gas cylinder, such asa high pressure, liquid carbon dioxide cartridge. The spraying devicemay be charged by the caregiver when he or she activates the chargedcanister of gas.

Once the dressing-to-skin and tube-to-dressing interfaces are sealed(either during dressing application or during its manufacture), thecaregiver should monitor the pump to assure that air is not leaking intothe system above a predetermined threshold, typically zero, step 1505,FIG. 33. This can be done visually, for example, by monitoring theexpansion of the pump (a.k.a., mechanical pump) or with an air leak testthat is further disclosed in the pump descriptions, or it can be sensedusing pressure sensors to detect the vacuum pressure over time(particularly, with a mechanical pump, if the pressure changescontinuously with internal pump volume). If too high of an air leakexists, the dressing-to-skin and/or tube-to-dressing interfaces can beresealed with the liquid sealant by removing the previously appliedsealant material, or overlaying the new sealant over the previouslyapplied seal material, step 1506, FIG. 33. This is an iterative processuntil the desired air leak threshold is achieved, step 1507.

When a truly occlusive wound dressing is used for NPWT, the behavior ofthe system changes from an active flow system, FIG. 34A, to a passiveflow system 1602, FIG. 34B. When air leaks, arrows 1603, FIG. 34A intothe active system, the system has an active flow of fluid (both air andwound exudate) that both removes the exudate from the wound cavity 1604and tends to dry out the wound cavity. With an air-tight system 1602,FIG. 34B, the flow of the exudate toward the pump is no longer an activeflow, but tends to build up, 1605, even into the tube over time,maintaining a passive flow to the vacuum source. A pressure differentialstill exists at the surface of the wound bed 1606 and, thus, negativepressure is still being applied to the wound bed; however, the woundcavity volume 1604 fills with exudate fluid 1605 over time. Thischaracteristic may have increased healing benefits compared to standardNPWT, as it maintains a moist, healing environment at the wound site,while also maintaining NPWT vacuum pressure benefits.

With this build-up of fluid 1605, FIGS. 34B and 35, the dressing-to-skininterface adhesion 1607 may be compromised over time by the exudate, andthe exudate may eventually undermine the dressing and leak out of thedressing-to-skin interface. The rate of exudate removal, size of thewound cavity, and time between dressing changes determine the build-upcharacteristics. If there is a chance that the dressing may becompromised, it can be prevented with multiple methods, including:

1) A sealant or additional adhesive that can withstand the exudatebuild-up may be applied. For this case, the sealant and/or additionaladhesive should be applied as close to the wound edge as possible. Thisis difficult if a standard dressing was used. Planar dressings typicallyleak over the three-day dressing period if fluid build-up occurs. Thisis because the exudate often degrades the adhesive by undermining thedressing at the wound edge at the locations of initial creases in thedressing. Therefore, a dressing without initial cracks at the wound edgeis preferred; however, the dressing application described in theprevious section only seals the outer edge of the dressing. To solvethis problem, a flexible adhesive, with flexibility and adhesiveproperties such as those of a 30+ day silicon wig glue, may be initiallyapplied at the wound edge under the adhesive planar dressing. This canfill in any initial cracks at the wound edge and prevent exudate-causeddegradation.

2) A barrier can be applied at the wound edge, after the wound packingmaterial is inserted. This barrier may be made of highly absorbentmaterial, in order to reduce the chance of overspill of exudate due tofactors, such as gravitational effects.

3) The tube end can be recessed into the wound cavity below the plane ofthe surface of the skin 1702, as indicated by arrow 1701, FIG. 35.Therefore, the drainage line of fluid 1703, and hence the build-up ofexudate will not build-up to the wound edge 1607, and degrade theadhesive. This technique may not be possible if the wound issuperficial.

4) A purge valve to let a controlled, temporary air leak into thedressing system to clear the fluid can be incorporated into the dressingsystem. This valve can be incorporated using the same connection methodsas described in the Tube-to-Dressing Interface section in thisdisclosure. This would cause the fluid to actively flow into the fluidcollection canister during the initial pressure drop in the system. Thepump can be reset, if necessary.

5) The wound packing material can be made from materials with a lowresistance to the flow of exudate and a low absorption, which wouldencourage the fluid to passively move through the system at a fasterrate in a path more direct to the drainage tube. Depending on the rateof exudate removal, this may not fix the problem if it is a very lowrate. In this case, the packing material should be designed to directflow to the drainage tube and specifically away from the wound edge.

6) If the dressing is fabricated completely out of the liquid sealant(potentially with an additional adhesive) with no planar dressingcomponent, then no cracks will exist at the wound edge when it isproperly applied, and therefore, no cracks will initially exist for theexudate to undermine.

Although any mechanical or electrical vacuum source may be applied tothe occlusive dressings in this disclosure, a mechanical system may bepreferred due to the significant benefits over electrical pumps.Mechanical vacuum pumps and methods are provided for medical applicationin negative pressure wound therapy (NPWT) that would be compatible withthe disclosed dressings. A number of known pumps are described by thepresent inventor in “Development of a simplified Negative Pressure WoundDevice” submitted in 2007 for her Master of Science in MechanicalEngineering at the Massachusetts Institute of Technology. The pump isinitially set and then governed by a linear or non-linear spring force.The pump enclosure may act as a collection chamber; however, a separatecollection chamber may exist in series with the pump.

In one embodiment, the pump is a plastic bellows, shown in FIG. 31,where the enclosure and spring can be the same component. The pump iscompressed manually and then attached to the tube of the wound dressing.A negative pressure is applied through expansion of the bellows due tothe spring characteristics of its material and design. The pressuregradient of the device continuously decreases over the expansion of thestandard bellows due to its linear spring-like properties. Referring tothe above description, one skilled in the art would realize that otherembodiments exist: the device could be constructed of a differentmaterial bellows, and/or the device could contain an additional spring 5in parallel with the bellows in order to vary the spring constantwithout changing the material properties and design of the bellowsitself. If there are no air leaks into the system, then the bellowswould remain at a constant expansion length, and therefore, at aconstant pressure. The bellows can be collapsed to any desired therapypressure from maximum compression to zero.

In addition to the standard bellows, another embodiment of bellows canresemble a constant force spring, in order to decrease the pressuregradient. In one embodiment of this design, the bellows resembles a longtube that, when fully compressed, is rolled onto itself, similar to atape measure, as shown in FIG. 32. As it unrolls and expands from itsflattened to open cross-section, it creates negative pressure in thetube to which it is connected. For the tube to unroll following theexpansion of the bellows, the spring constant of the bellows must behigher than the spring constant of the constant force spring unrolling.The unrolling can also be mechanically dampened, for example byadhesion, or forced to unroll after expansion by structural limiters. Inthis embodiment, a long, cylindrical tube can replace the bellows, as itpresents similar characteristics.

In all of the pumps described above, orientation of the device isindependent of the magnitude of negative pressure pulled and the properoperation of the device. Therefore, the device is highly transportable.Referring to the above descriptions, one skilled in the art wouldrealize that other embodiments exist; however, only selected embodimentsare described in detail. To change pressures in a pump design, separatepumps can be made with different material properties and/or dimensions,or components can be swapped for different pressure results.

The negative pressure generated is governed by the material andmechanical properties of the container and/or balloon and the springconstant. Using a non-constant force spring (such as a common linearspring 5, FIG. 31, the pump may be used for negative pressure woundtherapy that does not require a specific, constant pressure (in the casethat the internal volume of the pump is expected to expand), althoughthe variance in pressure can be reduced through material propertyselection and design. Using a constant force spring with a constantarea, a constant vacuum pressure can be pulled throughout treatment,even if there is a change in the internal volume of the pump. This isthe basis for design of the rolling bellows (FIG. 32), and the syringeconcept discussed in the next section. Additionally, a more constantpressure with pump expansion can be achieved with a non-constant forcespring by designing the force/area ratio to be constant, such as theballoon design with a small (constant) diameter to length ratio and abellows with a varying cross-sectional area. Additionally, constantpressure can be achieved over time if no air leaks into the system,causing geometrical changes in the pump configuration. In this case, thepumps should be made out of materials that do not degrade when applyingnegative pressure overtime due to properties such as stress relaxation.

The pump is initially set and then governed by gravity. It includes anexpansion container that expands due to an applied force such as aweight. The pump enclosure may act as a collection chamber; however, aseparate collection chamber may exist in series with the pump. In oneembodiment, the pump includes a rolling diaphragm syringe (similar to afriction free diaphragm air cylinder). Negative pressure amplitude isgoverned by the diameter of the syringe and the magnitude of theattached weight. One skilled in the trade would realize that a similardevice could also be constructed of any sealed piston syringe. Referringto the above descriptions, the device could also include a linear springin parallel with the syringe or a constant force spring in series withthe syringe for expansion, eliminating the need for weight. Thisembodiment would then fall under the spring governed pumps described inthe previous section. A rolling diaphragm can also be achieved using arubber ball design. One hemisphere of the rubber ball is held rigid inits inflated position, such as by bonding it to the inside of a rigidhemisphere, and the other hemisphere is compressed into it. Theembodiment of the pump resembles a bowl. Then, the bowl is oriented sothat its hollow side is facing down. A weight is hung from the ball(i.e., a rubber ball) on the hollow inside of the hemisphere, and thewound drainage tube is connected to the internal volume of the pump(preferably through the top of the rigid hemisphere). The weight pulls anegative pressure as the ball returns back to the shape of a sphere.

Another embodiment for a gravity governed pump is created by a siphon.The pump enclosure may act as a collection chamber; however, a separatecollection chamber may exist in series with the pump. The pressurepulled is equal to:

rho*g*h  (2)

wherein rho is the density of the fluid in the column, g being thegravitational constant, and h being the height of the column). The fluidshould be compatible with the wound (such as saline), unless a checkvalve is used to assure separation of the pump fluid from the woundcavity. The pump can be configured in two ways, depending on the patientsituation and the desired pressure:

1. The pump can include a column of fluid that exists in a tube directlyconnected to the wound. The lower (preferably closed-expandable)container of fluid can rest at the desired height on a separatemechanism (such as a hanging hook or floor), or could be attached to alower extremity of the patient, again at the desired height. Thediameter of the tube would determine the pressure gradient: the largerthe diameter, the lower the pressure gradient as fluid is collected.

2. The pump can include two bodies of fluid with a tube from the higherbody of fluid to the wound. The mobility of the patient would bedetermined by the tube length and the mechanism used to carry the pump(for instance, a rolling stand could be used). The diameter of thehigher container would determine the pressure gradient: the larger thediameter, the lower the pressure gradient as fluid is collected.

Integrating the spring governed pumps with the gravity governed conceptallows for further performance. Then, the magnitude of negative pressurea spring governed pump can obtain is not completely limited by thematerial properties of the container, the design, and the springconstant combination. Additional weights can be attached to one end ofthe pump in series with the spring, in order to pull a higher negativepressure. (For the bladder concept, portions of the bladder may needstructural support, so that the bladder does not collapse on itself asthe weight acts on it.) The weights should be attached between the pumpand ground. Even though in this form the orientation of the pump shouldbe maintained, varying the additional weight is a simple solution toachieving multiple pressures beyond that of the original pumpproperties.

A container evacuation pump is not continuously governed by a forceexerted on the container. Instead, the pump is simply an evacuated rigidchamber that is continuously monitored through a pressure gauge, such asgauge 4 in FIGS. 31 and 32. Alternatively, a mechanical check gaugewould be used, with an optimal pressure range. When the vacuum pressuredecreases to a certain, predetermined level, a notification mechanism isactivated and the rigid chamber is recharged. Recharging can be by apump or by human suction. In this embodiment, the rigid chamber can actas the collection container, or a separate non-structural, expandablecontainer can be inserted into the rigid chamber that is directlyconnected to the wound drainage tube. An expandable collection chambercan be integrated into any of the mechanical pump concepts disclosed inthis disclosure, in order to collect the fluid inside the pump body,acting as a collection liner instead of a completely separate collectioncanister.

To administer NPWT, the pump is connected to the wound drainage tube,and the container is then evacuated. Air leaks and wound drainage ratedetermines the pressure gradient, and the pressure range is determinedby the maximum pressure pumped and the recharge notification pressure.The maximum pressure pumped can be limited by a pressure activated inletvalve.

As generally applies to all of the above-mentioned pumps, a sequence ofsteps should be followed. First, the tube connected directly to thedressing should be clamped shut between the dressing and the collectionchamber, preferably at the collection chamber end. Then, the pump andcollection chamber should be disconnected. If necessary, the collectionchamber should be emptied, and/or the proper sterilization proceduresshould be performed; component 8, FIG. 31, represents a rubber plug, notshown because integral floor 260 is utilized instead, for increasedaccess to the interior of the collection chamber in an alternativeconstruction. The pump should then be reset, and the pump and collectionchamber reconnected to the tube. Remove the clamp to begin NPWT again.If a dressing change is also desired, there is no need to use a clamp tokeep the dressing sealed. Also, if the collection chamber does not needto be emptied and/or sterilized, then the tube should be clamped betweenthe dressing and the pump, preferably after the collection chamber if itis separate from the pump at the pump end of the tube.

An air leak test can be incorporated into the mechanical pumps, exceptfor the first (1) siphon concept. In the second (2) siphon concept, thehigher container is turned upside-down for the initial air leak test.Most air leaks originate at the dressing interfaces. In a purelymechanical pump, air leaks fill the limited volume, causing the maximumtime between pump resets to decrease. To eliminate these air leaks andcreate a reliable, repeatable therapy, devices according to the presentdisclosure may include an air leak test. By using the air leak test, thepurely mechanical pumps have been proven to be capable of lastingthroughout the recommended timeframe between dressing changes (3 days).However, this test is not necessary for the occlusive seals anddressings disclosed in this disclosure, but can provide a visualreassurance to the caregiver and patient that the dressing was appliedproperly and no significant leaks exist in the system.

The air leak test is in the collection chamber. The tube from the woundthat enters into the collection chamber enters into a wound compatiblesolution (such as saline). When applying the NPWT, one should confirmthat the end of the tube is submerged in the solution and should look atthe solution for air bubbles B, FIGS. 31 and 32, (any air that initiallyexists in the tube may create air bubbles; therefore, one should waitabout 1-2 seconds for additional air bubbles). If air bubbles aredetected, the dressing should be sealed until no air bubbles aredetected. This resealing may be to completely redress the wound, tosmooth out the air leaks in the current dressing, or to reinforce thecurrent dressing with additional dressing components. Once no airbubbles are detected, the pump may need to be reset depending on howmuch air entered into the pump.

A safety feature of the collection chamber is to limit the amount ofliquid capable of being collected. If the collected liquid were blooddue to destruction of a vein or artery, there exists a possibility thatthe patient may die due to fatal bleeding. The collection chamber shouldbe limited to less than 300 cc of liquid to keep the patient at a saferange from possible exsanguination. Therefore, if the pump design canpull more than 300 cc of fluid, a safety feature should be implemented.If the pump acts as the collection chamber, the safety feature shouldlimit its expansion volume. This can be done in various ways through theintroduction of limiting, internal (FIG. 31, component 6) and/orexternal (FIG. 31, component 7) structural components. If an externalcollection chamber exists, then a safety feature should stop thenegative pressure after 300 cc is collected. This can be done by“plugging” the system with a mechanism, such as a float-stop valve.

Prior to the existence of a truly occlusive dressing, a benefit in theexternal collection chamber was that the pump can be larger than 300 cc,and therefore, account for more air leaks into the system. However, witha truly occlusive dressing, the benefits include that the externalcollection chamber and its fluids can be easily removed for lab testingpurposes, and the pump requires a less rigorous cleaning procedurebetween dressing changes. However, these benefits are more readilysolved with a volume specific container with no rigidity, and containingno initial volume of fluid that may contaminate a exudate sample, ifdesired, that can be inserted into any of the mechanical pump conceptsdisclosed in this disclosure, in order to collect the fluid inside thepump body, acting as a collection liner instead of a completely separatecollection canister. The 300 cc limitation is recommended for theaverage adult; however, the limitation volume may vary based on thepatient. This volume variation can be designed into multiple pump orcollection chamber sizes, or into a single, limit adjustable pump orcollection chamber.

Another pump safety feature is a one-way valve incorporated in the tubebetween the wound and the collection chamber, such as component 2, FIGS.31 and 32. This mechanism assures that fluid from the pump andcollection chamber does not flow back into the dressing. It also can beused as the tube clamping mechanism for resetting the pump or emptyingthe collection chamber, depending on placement in the tube. Thismechanism can also be incorporated into the tube connector on thecollection chamber.

Another mechanism that may be included is used to evacuate the initialair found in the system after no air leaks are detected. The currentmethod is to clamp the tube near the pump and to reset the pump untilthe initial air is evacuated from the system. This can also beaccomplished by including a one-way-valve incorporated into the tubeconnector on the pump, such as component 2, FIGS. 31 and 32, and anotherone-way-valve incorporated between the interior cavity of the pump andatmosphere, component 3, shown with a cap C in FIG. 31. With thisdesign, one can continue to compress (reset) the pump until the desiredvacuum is maintained; the system does not need to be disconnected. Theone-way-valve open to atmosphere can be capped after therapy begins.

This mechanism cannot be easily integrated to eliminate the need forresetting the pump in the design that includes a rubber balloon that isinserted into an orifice of an air-tight container and the two siphonpumps. For the balloon design, a connection to the container can be madeto incorporate the attachment of a separate pump with the one-way-valveand check valve design. This pump can be attached for initial ballooninflation and container evacuation, and then detached between dressingchanges. In the two siphon concepts, a pump can be attached to evacuatethe space above the column of fluid, raising the fluid level to thedesired height. The pump can be detached for extended therapy, betweendressing changes.

An individual sealant component may be packaged by itself to make anyskin dressing occlusive. Alternatively, the sealant can be packaged aspart of a mechanical NPWT kit, including a mechanical pump and itspre-attached components, tubing with flexible foot and pre-attachedtubing connector and optional one way valve, dressing adhesive film tocover the packing material (if necessary), the sealant material in ahandheld spray container, a wound packing material, and skin prep (ifnecessary). Additionally, if there is an adhesive dressing tape-likefilm that should be handled by the caregiver, then non-stick fingertipcovers maybe included for better adhesion outcomes. Non-powdered glovesmay also be included, so that the Van der Waals forces for sealantattachment are not altered due to powder on the skin surface. Oneskilled in the art would realize that kit components may be swapped fortheir different functional embodiments, discussed above. Also,additional components may be added or put into additional kits that areused in typical dressing changes, such as wound debridement tools, oradditional wound therapies, such as medications with their correspondingintroduction and (potentially) removal ports through the dressing, intothe wound cavity.

As many dressing systems are identified in this disclosure, one skilledin the art would realize that the liquid sealing method can be used incombination with any tissue (a.k.a., skin) dressing in order to createan air-tight seal. As many pumps are identified in this disclosure, oneskilled in the art would realize that any pump combined with theocclusive dressing systems would have similar performancecharacteristics.

One technique according to the present invention for constructing anocclusive dressing over a wound includes at least one of (1) packing thewound with a fluid-pervious material and (2) covering at least a portionof the wound with a protective material. The method further includesapplying, such as by spraying, an organic material, preferablyelastomeric, that is in a liquid state, and is at least partiallycross-linked at least after one of drying and curing, over the packedmaterial and onto skin surrounding the wound to create an occlusivedrape as a thin sheet substantially impervious to fluid transfer, havinga first, inner surface and a second, outer surface. As utilized herein,the term “organic material” includes matter in various forms thatinclude carbon atoms, including silicone rubbers. The method includes atleast one of drying and curing the elastomeric material within thirtyminutes after application of the elastomeric material as a layer.

FIG. 38 is a schematic top plan view of the wound shown in FIG. 14, herewith a cleaned skin zone indicated by dashed line 302 and with packingmaterial 304, such as gauze or a sponge. Additionally, a protectivecovering material 306 is applied over the wound when intended liquiddrape material has a sufficiently lower viscosity and longer set time tobe absorbed into the packing material 304. Protective material 306prevents liquid drape material from flowing into the wound cavity. Insome constructions, protective material 306 is a solid impermeable orsemi-permeable polymeric sheet, which may be utilized with or withoutadhesive. In other constructions, protective material 306 is a clay-likesubstance that can be molded and packed over packing material 304 andaround a tube inserted into the packing material 304.

FIG. 39 is a view of FIG. 38 with a hole 308 cut in the protectivecovering 306, if an opening in the protective covering 306 has notalready been formed or maintained.

FIG. 40 is a view of FIG. 39 with a tube assembly 27 c, with tube 24 cand flange 26 c, having sleeve 52 d, rotation region 54 d and adhesionregion 56 d, placed over the hole 308. Tube assembly 27 c is maintainedin position with adhesive in some techniques and, in other techniques,is manually held in place. Alternatively, tube 24 c can directlypuncture protective covering 306 such that covering 306 maintains atight seal around tube 24 c, potentially with an additional seal barriersuch as clay or adhesive. In another construction, flange 26 c issufficiently large in diameter to completely cover the wound.

FIG. 41 is a view of FIG. 40 with liquid drape material 310 applied overthe protective covering 306 and onto surrounding skin SK to cover skinzone 302 to thereby construct a dressing according to the presentinvention. The liquid drape material 310 is applied by spraying orapplication technique such that material 310 firmly attaches to skin SKsurrounding the wound and covers any protective cover layer 306, ifutilized, as well as creating an air-tight seal around flange 26 d. FIG.42 is a schematic perspective view of the dressing of FIG. 41 In otherconstructions, the drape is constructed directly onto a tube withoututilizing a separate flange.

FIG. 43 is a schematic perspective view of a novel flange 26 d accordingto the present invention with integral connector 320 having a barb-typeengagement feature 322 defining passage 324. Engagement feature 322 isinsertable into end of a tube.

Although specific features of the present invention are shown in somedrawings and not in others, this is for convenience only, as eachfeature may be combined with any or all of the other features inaccordance with the invention. While there have been shown, described,and pointed out fundamental novel features of the invention as appliedto one or more preferred embodiments thereof, it will be understood thatvarious omissions, substitutions, and changes in the form and details ofthe devices illustrated, and in their operation, may be made by thoseskilled in the art without departing from the spirit and scope of theinvention. For example, it is expressly intended that all combinationsof those elements and/or steps that perform substantially the samefunction, in substantially the same way, to achieve the same results bewithin the scope of the invention. Substitutions of elements from onedescribed embodiment to another are also fully intended andcontemplated. It is also to be understood that the drawings are notnecessarily drawn to scale, but that they are merely conceptual innature. It is the intention, therefore, to be limited only as indicatedby the scope of the claims appended hereto. Other embodiments will occurto those skilled in the art and are within the following claims.

1. A kit suitable for occlusively sealing a wound penetrating the skinof a patient, comprising: a drape formed as a thin sheet of an organicmaterial substantially impervious to fluid transfer and having first andsecond surfaces; an interface including at least one of (i) a flexibletube having a first end extendable through the drape and having a secondend connectable to a source of negative pressure, (ii) at least twopieces of drape capable of forming a joint through which a first end ofa tube is insertable, and (iii) a flange attachable to a tube; abiocompatible adhesive that is at least one of (1) disposed on at leasta portion of the first surface of the drape and (2) capable ofcontacting at least a portion of at least the first surface of thedrape; when the kit includes the biocompatible adhesive disposed on atleast a portion of the first surface of the drape, the kit furtherincludes at least a first removable liner sheet covering the firstsurface of the drape; and at least one container of at least one sealantcomponent that is capable of being delivered as a sealant in a liquidstate at pre-selected ambient conditions, the sealant as delivered beingat least partially cross-linked at least after one of drying and curing,and which is capable of at least one of drying and curing within thirtyminutes after application of the sealant as a layer to the edges of thedrape after the drape is applied to the skin surrounding the wound. 2.The kit of claim 1 wherein the organic material and the sealant afterone of drying and curing are elastomeric.
 3. The kit of claim 1 whereinthe drape and the sealant are derived from substantially the samematerial.
 4. The kit of claim 1 wherein at least a majority of the drapeand the sealant are derived from a type of a latex compound.
 5. The kitof claim 1 wherein at least a majority of the drape and the sealant arederived from a type of a silicone compound.
 6. The kit of claim 1wherein the adhesive is a silicone-based adhesive.
 7. The kit of claim 1wherein the adhesive is disposed on at least a majority of each of thefirst and second surfaces of the drape.
 8. The kit of claim 1 furtherincluding a flexible tube having a first end and having a second endconnectable to a source of negative pressure.
 9. The kit of claim 8wherein the interface includes at least one of (1) a flange having acentral passage through which the first end of the tube is insertableand (2) a flange having a central passage communicating with a connectorcapable of mating with the first end of the tube.
 10. The kit of claim 8wherein the first end of the tube includes a feature to resist blockageof the tube.
 11. The kit of claim 8 further including a mechanical pumpcapable of serving as the source of negative pressure.
 12. The kit ofclaim 11 wherein the mechanical pump is a bellows-type pump capable ofbeing rolled upon itself and then unrolling to exert negative pressure.13. The kit of claim 1 wherein the at least one container of at leastone sealant component is a cartridge removably insertable into adispensing apparatus.
 14. The kit of claim 1 wherein the at least onecontainer of at least one sealant component is squeezable to deliver thesealant.
 15. The kit of claim 1 further including at least one woundpacking material. 16-34. (canceled)
 35. A kit suitable for occlusivelysealing a wound penetrating the skin of a patient, comprising: a drapeformed as a thin sheet of an organic material substantially imperviousto fluid transfer and having first and second surfaces; a biocompatibleadhesive that is at least one of (1) disposed on at least a portion ofthe first surface of the drape and (2) capable of contacting at least aportion of at least the first surface of the drape; when the kitincludes the biocompatible adhesive disposed on at least a portion ofthe first surface of the drape, the kit further includes at least afirst removable liner sheet covering the first surface of the drape; andat least one container of at least one sealant component that is capableof being delivered as a sealant in a liquid state at pre-selectedambient conditions, the sealant as delivered being at least partiallycross-linked at least after one of drying and curing, and which iscapable of at least one of drying and curing within thirty minutes afterapplication of the sealant as a layer to the edges of the drape afterthe drape is applied to the skin surrounding the wound, wherein the atleast one container of at least one sealant component is a cartridgeremovably insertable into a dispensing apparatus.
 36. The kit of claim 1wherein the adhesive is an acrylic-based adhesive.